Method for molding a composite with an integrally molded rib

ABSTRACT

A technique is provided for both forming frame portions from thermoplastic resin prepregs containing randomly arranged reinforcing fibers directly at predetermined location(s) upon a preformed wall portion and simultaneously bonding such as formed frame portions directly to such wall portion at such location(s). The wall portion is itself a laminate derived from thermoplastic resin prepregs containing ordered, substantially continuous reinforcing fibers.

BACKGROUND

1. Field of the Invention

This invention lies in the field of manufactured articles comprised offiber reinforced engineering resin laminated composites, and includesapparatus and methods for making such articles from preformed prepregs.

2. Prior Art

In the art of composites, it is common to prepare prepregs of so-calledengineering resins and reinforcing fibers. From the prepregs, composites(including laminated composites) are prepared.

To fabricate composites from prepregs, various forming techniques can beused, such as a so-called stamp molding procedure or the like, thetechniques typically employing elevated temperatures and pressures. Theart of fabricating composites from prepregs is relatively young and ischaracterized by unsolved fabrication problems. A problem has existed,for example, in forming three-dimensional, integral one-piece compositestructures which are comprised of two different types of startingprepregs, a first type being identified herein as a first prepreg typewhich comprises a resin layer generally uniformly impregnated with anarrangement of substantially continuously extending ordered fibers, in aform such as a woven fabric, or a unidirectionally arranged array ofspaced, parallel continuous fibers, and a second type being identifiedherein as a second prepreg type which comprises a resin layer generallyuniformly impregnated with substantially randomly arranged reinforcingfibers, in a form such as a fiber mat, or randomly dispersed choppedfibers. The first such type of prepreg is well suited for use in themanufacture of flattened components to be used as wall portions or othersimilar flattened members, while the second such type of prepreg is wellsuited for use in the manufacture of three dimensional components to beused as frame or supporting portions or other similar projectingmembers. Such three-dimensional components preferably have a baseportion that is securable to such a wall portion and also one or moreintegrally formed raised or projecting and upstanding portions, such asrib, frame, and support members, brackets, flanges, projections,platforms, and the like.

The principle reason for the differences in suitability between theserespective first and second prepreg types arises out of the circumstancethat the first such type of prepreg is difficult to mold into threedimensional members incorporating a major raised projection becauseordered continuous reinforcing fibers in a prepreg are found to bedifficult to stretch or elongate to an extent such as may be necessaryto produce a product composite having undamaged fiber reinforcement in aprojecting portion (depending, of course, somewhat upon the location andheight of the raised portion relative to the adjacent surrounding baseregions). However, in a prepreg, such as one of the second typecontaining a randomly arranged mat of fibers, there is a demonstratedcapacity under the application of heat and pressure for both resin andreinforcing fiber to move transversely in a base region and outwardlyaway from the base region along with the impregnating resin, therebypermitting production of a product composite having a desired threedimensional structure which is substantially fully fiber reinforced.

A two-step composite manufacturing procedure, where, for example, acomposite wall component is fabricated in one operation or step, andcomposite frame components (for supporting and rigidifying the wallcomponent) are fabricated in another operation or step, and then theresulting respective components are somehow adhesively bonded ormechanically fastened together, is generally objectionable. For onething, it is difficult to get a close fit between two such separatelyfabricated different composite components. Because of the rigidity andstrength characteristically associated with composite components atambient temperatures and pressures, fits and fit adjustments aredifficult to achieve. For another thing, the surface characteristics offabricated composite components make it difficult to adhesively bondsuch together using, for example, an adhesive substance which is appliedbetween interfacially contacted component surfaces in a separate stepafter component fabrication. For another thing, the toughness of therespective separately fabricated components makes it difficult, and alsotime and labor consuming, to fasten such securely together by mechanicalmeans, such as by rivets, nut and bolt assemblies, or the like.

The art of composite manufacture needs an improved technique for makingintegrated composite structures incorporating both above-indicated firstand second types of fiber reinforced prepreg structures wherein eachtype is used to make respective component portions for which it is bestsuited.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a new and very usefulmolding process of the stamp molding type for fabricating integrallyassociated single-piece laminated composite structures incorporating twodifferent prepreg types with each respective prepreg type being utilizedto form a composite structure for which it is well suited, a first suchprepreg type being used for forming flattened wall portions and beingimpregnated with spatially ordered continuous reinforcing fibers, and asecond such prepreg type being used for forming raised orthree-dimensional frame portions and being impregnated with randomlyarranged reinforcing fibers, both such prepreg types utilizing ahigh-performance, thermoplastic resin as the matrix phase.

Another object of the present invention is to provide a new and usefulclass of multiple component mold structures adapted for use in thefabrication of single-piece, integrally-formed, laminated compositestructures having both wall portions and frame portions, with each suchrespective such portion incorporating a different type of preform.

Another object of the present invention is to provide a new and improvedclass of single-piece, integrally-formed, three-dimensional laminatedstructural composite, made from prepregs incorporating ahigh-performance thermoplastic resin matrix and reinforcing fibers. Insuch composite, the wall portions are derived from fiber reinforcedpreforms that incorporate ordered continuous reinforcing fibers, whilethe frame portions are derived from fiber-reinforced preforms thatincorporate randomly arranged reinforcing fibers.

Other and further objects, aims, purposes, features, advantages,embodiments, and the like will be apparent to those skilled in the artfrom the teachings of the present specification, taken with theassociated drawings, and the appended claims.

More particularly, in one aspect, the present invention relates amolding process for manufacturing an integrally formed laminatedstructural composite from two different types of prepregs both comprisedof fiber reinforced, high-performance thermoplastic resin, a first suchprepreg type incorporating an ordered arrangement or pattern comprisedsubstantially of continuous reinforcing fibers, and a second suchprepreg type incorporating a random arrangement of reinforcing fiberswhich can be continuous or not, wherein wall portions of the laminatedstructural composite are preformed and derived from such first prepregtype, while frame portions of the laminated structural composite arederived from such second prepreg type but are produced (formed) andbonded to the wall portion in a single operation. By using such process,manufacturing of such a laminated structural composite is accomplishablein two successive molding procedures (one to make the wall portion, andanother for forming and bonding the frame portion) without the use ofany auxiliary adhesive means, and without the use of any auxiliarymechanical fastening means.

In another aspect, the present invention relates to three-component moldstructures which are useful in the practice of the composite formationprocess above characterized.

In another aspect, the present invention relates to a class ofintegrally formed, molded, laminated structural composites whichcharacteristically incorporate two different types of prepregs, bothprepreg types being comprised of fiber reinforced, high-performancethermoplastic resin. A first such prepreg type incorporates orderedcontinuous reinforcing fibers, while a second such prepreg typeincorporates randomly arranged reinforcing fibers. Composite wallportions are derived from such first prepreg type, while composite frameportions are derived from the such second prepreg type. Such structuralcomposites are produced by using the above indicated molding process andmold structures.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an isometric view of one embodiment of a laminated structuralcomposite of the present invention;

FIG. 2 is a side elevational view of one embodiment of an assembledthree-component mold assembly adapted for use in the making of thecomposite of FIG. 1;

FIG. 3 is a vertical sectional view taken along the line 3--3 of FIG. 2;

FIG. 4 is a vertical sectional view taken along the line 4--4 of FIG. 3;and

FIG. 5 is an exploded perspective view of the mold assembly of FIG. 2.

FIG. 6 is an exploded perspective view of a mold assembly adapted forpositioning in any press such as a Lawton Press Model 300 Ton for use inmaking a three-dimensional structural composite of the presentinvention; and

FIG. 7 is a perspective view of one embodiment of a three-dimensionalstructural composite of the present invention.

DETAILED DESCRIPTION PREPREGS

For present purposes, a prepreg can be regarded as a fiber reinforced,self-supporting, heat and pressure processable layer comprising anengineering resin. Such layer is in a sheet, film, ribbon, or likephysical form wherein reinforcing fibers associated with such resin arethemselves in various physical forms, such as a woven fabric, anon-woven web or mat, unidirectionally arranged monofilaments, yarns,roving, chopped fiber, pulp, spun-laced sheet, wet-laid paper, and thelike. As indicated above, physical properties in product composites insheet or laminated form are generally improved and even maximized byusing continuous fibers which are systematically arranged or ordered inthe starting prepregs, such as unidirectional or woven reinforcingfibers. Also, as indicated above, moldability of a starting prepregdirectly into a three dimensional fiber reinforced object is enhanced byusing starting prepregs wherein the fiber is randomly ordered.Conventionally, and in general, the quantity of total fiber in a prepregranges from about 10 to 90 weight percent, while the quantity ofthermoplastic resin ranges inversely from about 90 to 10 weight percent(on a 100 weight percent total prepreg basis). Various techniques areknown for making prepregs of fiber reinforced high-performancethermoplastic resins.

As those skilled in art will readily appreciate, any known prepregforming method can be utilized in the preparation of the respectivefirst and second prepregs used as starting materials in the practice ofthe invention. In general, the known methods are adaptable for use inmaking both types of prepregs. Examples of suitable methods include, butare not limited to, (a) a slurry (usually aqueous) impregnationprocedure for making stackable sheets such as disclosed in Still et alU.S. Pat. No. 4,522,875, (b) a pultrusion process such as disclosed inO'Connor U.S. Pat. No. 4,680,224, (c) a compaction belt method such asdisclosed in Ma U.S. Pat. No. 4,622,192, and (d) an extrusion compactingroller process such as disclosed in Della Vecchia et al U.S. Pat. No.4,269,884, and the like.

Thermoplastic Resins

The thermoplastic resins that are suitable for use in the practice ofthe present invention conform generally to the definition of"engineering plastics" provided by the Kirk-Othmer Encyclopedia ofChemical Technology (3rd ed., Vol. 9, Wiley-Interscience, New York,1980, P118).

In terms of properties, engineering plastics have a good balance of hightensile properties, stiffness, compressive and shear strength, as wellas impact resistance, and they are easily moldable. Their high physicalstrength properties are reproducible and predictable, and they retraintheir physical and electrical properties over a wide range ofenvironment conditions (heat, cold, chemicals). They can resistmechanical stress for long periods of time.

acetal resins,

polyamides,

polyimides,

polyamide imides

polyether imides

polyethers,

polyesters,

polycarbonates,

polyarylene sulfides

polysulfones, such as polyarylsulfones

polyketones,

and the like. Any one of such respective generic resins can include inits backbone structure other linking moieties that join togetherrepeating units besides the linking moiety designated in its name. As aconsequence, the distinctions between different generic resins canbecome indistinct, as those skilled in the art readily appreciate.

For example, in the case of polyethers, residues of various startingmonomers can be linked with non-ether linking groups and such othermoieties when present produce various recognized polyether polymerclasses, such as polyarylethers (really an all-ether linked polymer),polyether ketones, polyetherether ketones, polyether diketones,polyether sulfones, polyether imides, and the like. Polyarylethers areavailable commercially, for example, from the du Pont Company under itstrademark "ARALON", and from the Amoco Performance Products Co. underthe trademark "RADEL C". Polyether ketones (sometimes known as "PEK")are commercially available from ICI Americas under its "VICTREX"trademark, from BASF under its trademark "ULTRAPEK ,"and from Hoechstunder its trademark "HOSTATEC". Polyetherether ketones (sometimes knownas "PEEK") are available commercially, for example, from ICI Americasunder its "VICTREX" trademark. Polyether diketones (sometimes known as"PEKK") are believed to be available commercially from the du PontCompany (trademark or tradename presently unknown). Polyether sulfones(sometimes known as PES) are commercially available from ICI Americasunder its "VICTREX" trademark, and are believed to be availablecommercially from the Amoco Performance Products Company under itstrademark "RADEL X."Polyether imides (sometimes known as "PEI") arebelieved to be available commercially from the General Electric Companyunder its trademark "ULTEM."

For another example, in the case of polyarylene sulfides, variousstarting monomers and various non-sulfide linking groups can beinvolved. When, for example, polyarylene sulfides (sometimes known as"PAS") are considered, various polymer classes can be identified, suchas polyphenylene sulfide (sometimes known as "PPS"), polyarylene sulfideketone (sometimes known as "PASK"), polyarylene sulfide sulfone(sometimes known as "PASS"), poly biphenylene sulfide (sometimes knownas "PBPS"), and the like. Characteristically, a polyarylene sulfidepolymer contains a plurality of units (which can be considered to berepeating units but which may not be in adjacent relationship to oneanother in a polymer backbone chain) of the formula:

    --S--Ar--

where "S" is a divalent sulfur atom, and "Ar" is a residue from anaromatic starting monomer of the formula:

    X--Ar--X

where "X" is a halogen selected from the group consisting of chlorine,fluorine, bromine and iodine, and where "Ar" is selected from the groupcomprising: ##STR1##

Polyphenylene sulfide resins are available from Phillips 66 Companyunder the trademark "RYTON."Polyarylene sulfide ketone resins can beprepared by the teachings of Gaughan U.S. Pat. No. 4,716,212.Polyarylene sulfide sulfone resins can be prepared by the teachings ofCampbell U.S. Pat. No. 4,127,713. Poly binphenylene sulfide and otherpolysulfide resins can be prepared by the teachings of Edmonds, Jr. andHill, Jr. in U.S. Pat. No. 3,354,129. Polyarylene sulfides are preferredthermoplastics for use in the practice of this invention.

Polyimides are available commercially, for example, from the duPontCompany under its tradename J 2.

Polyamides are available commercially, for example, from the duPontCompany under its tradenames K II and K III, and from the Mitsui Companyunder the trademark "LARC TPI."

Polyamide imides (sometimes known as "PAIs") are commercially available,for example, from Amoco Performance Products under the trademarks"TORLON" and AI-10.

Polyketones are available commercially, for example, from the AmocoCompany under its tradename HTX (believed to be a polyarylene ketone).

Polysulfones are available commercially, for example, from AmocoPerformance Products, Inc. under the trademark "UDEL."

Polyarylsulfones are available commercially, for example, from AmocoPerformance Products, Inc. under the trademarks RADEL and ARDEL.

Thermoplastic polyesters include (a) terephthalate polyesters, such aspolyethylene terephthalate (sometimes known as PET), polypropyleneterephthalate (sometimes known as PBT), copolymers thereof, and mixturesthereof, (b) liquid crystal polyesters, and the like. Polybutyleneterephthalate is available commercially, for example, from the GeneralElectric Company under the trademark VALOX. Polyethylene terephthalateis available commercially, for example, from Goodyear Tire and RubberCo. under the trademark CLEARTUF. Reinforced polyethylene terephthalateis available from such companies as du Pont (trademark: RYNITE),Allied-Signal (trademark: PETRA), Hoechst Celanese (trademark: IMPET),General Electric (trademark: VALOX), Mobay (trademark: PETLON),Thermofil, and Wilson Fiberfil (trademark: TETRAFIL). Liquid crystalthermoplastic polyesters (sometimes known as "LCPs") are available fromDartco Manufacturing under the trademark XYDAR, and from HoechstCelanese Corp. under the trademark VECTRA.

Alloys and blends of such thermoplastic resins can be used in thepractice of the present invention provided the blend or alloy hasperformance characteristics as above indicated for an "engineeringplastic."Typically, such a blend or alloy contains at least 2 of suchthermoplastic resins each present in a total concentration greater thanabout 5 weight percent (on a 100 weight percent total alloy or blendbasis excluding fiber reinforcement). The principal reason for blendingor alloying is to improve the resin cost/performance for a specific enduse application, as those skilled in the art appreciate. Specificparameters that may be improved by alloying include, for examples,impact, lubricity, chemical resistance, weatherability, heat, strength,flow, melt strength, and tear resistance. Alloys and blends areconventionally prepared by mixing two or more polymers together in amolten state. Sometimes an alloy can be prepared by two differentthermoplastic resins only one of which has properties satisfying the"engineering plastic" definition above given; even so, the alloy canhave properties satisfying such definition. Such alloys are suitable foruse in the practice of this invention.

Examples of suitable alloys for use in the practice of this inventioninclude ABS/polyamide, ABS/polyvinyl chloride/thermoplastic polyester(where "ABS" refers to copolymers of styrene, butadiene, andacrylonitrile, usually discrete polybutadiene particles dispersed in aglassy matrix of styrene and acrylonitrile copolymer), acetal/elastomeralloys, such as those available from the du Pont Company commercially,polycarbonate/polybutylene terephthalate alloys, andpolycarbonate/polyethylene terephthalate alloys, especially those whichalso contain one or more elastomers; polybutyleneterephthalate/polyethylene terephthalate alloys; polymeric elastomeralloys with polyethylene terephthalate and/or polybutyleneterephthalate; polyethylene terephthalate/polysulfone alloys (especiallythose which are reinforced with fibers, such as glass or the like),polyphenylene ether/high-impact polystyrene alloys (where high-impactpolystyrene (or HIPS) comprises a thermoplastic resin produced fromstyrene monomer with elastomers, commonly polybutadiene, beingintroduced into the polymer matrix); polyphenylene ether/polyamidealloys; polyphenylene sulfide/polytetrafluoroethylene alloys; and thelike.

As those skilled in the art appreciate, virtually all commerciallyavailable thermoplastic materials include additives, such as lubricants,stabilizers, fillers, fiber reinforcement agents, impact modifiers,flame retardants, colorants, anti-microbial agents, and the like. Theusage of such additives is intended to produce in a particularthermoplastic resin system an optimum property combination and/orprocess profile for specific applications. For example, most impactmodifiers known or available commercially are polymeric in nature, butpreferred impact modifiers for use in the practice of this invention arethermoplastic and have performance characteristics as above indicatedfor an "engineering plastic."So-called engineering thermoplasticelastomers (sometimes termed ETEs) which also have such performancecharacteristics can, for example, be incorporated into a starting resinblend or alloy for use in the practice of this invention. Like thesuitable thermoplastic resins above characterized and illustrated, ETEsare suitable for use under conditions of high load and creep potential,and have a broad service-temperature range, and are resistant tochemicals. Copolyester elastomers are most common and are preferred.Copolyester resins are available commercially from the du Pont Companyunder the trademarks HYTREL, and BEXLOY V, from Eastman ChemicalProducts under the trademark ECDEL, from Hoechst Celanese under thetrademark RITEFLEX, and from the General Electric Company under thetrademark LOMOD. If and when employed, the total amount of additives(including impact modifier and/or elastomer) present in a thermoplasticresin employed in the practice of this invention is usually less thanabout 15 weight percent based on the total weight of thermoplastic resinplus additive(s).

Reinforcing Fibers

Suitable reinforcing fibers adapted for use in the practice of thisinvention include those comprised of carbon, (including graphite)aramid, glass, quartz, silicon carbide, ceramic, metal coated carbon,metal (such as stainless steel, boron, copper, nickel, and the like),mixtures thereof, and the like. Such fibers are generally available fromvarious suppliers. Presently preferred such fibers include carbon,glass, and aramid.

The diameter of the reinforcing fibers typically ranges from about 10 to500 microns, but larger and smaller diameter fibers can be used. Apresent preference is to employ reinforcing fibers having averagediameters in the range from about 20 to 100 microns.

For reasons of maximum strength properties, substantially continuousfibers are preferred when woven fabric and unidirectional fibers areemployed for fiber reinforcement in starting prepregs having orderedfiber arrangements. In starting prepregs having random reinforcing fiberarrangements, continuous fibers are preferred for strength reasons inthose prepregs having an incorporated (impregnated with resin) fiber mator equivalent. However, discontinuous reinforcing fibers can be used insuch prepregs, and, when used, such fibers preferably have an averagelength of at least about 1 inch. Broadly, reinforcing fibers having alength down to about 1/8 inch (0.3 centimeter) can be employed.Preferably, the average length of randomly arranged or ordereddiscontinuous fibers used in a prepreg is at least about 10 times theaverage diameter thereof, and is more preferably at least about 15 timesthe average diameter thereof, although higher and lower minimum diameterto length ratios can be employed without departing from the spirit andscope of the invention. The term "diameter" as those skilled in the artwill appreciate, refers to the width dimension of fiber and such widthdimension need not be cross-sectionally circular. In practice thecross-sectionally circular. In practice the cross-sectionally fiberconfiguration can be of widely varying form such as elliptical,rectangular, etc. Hence, in estimating a diameter, an average value istaken for reasons of technical accuracy.

The fibers, whether spatially oriented in an ordered or randomconfiguration, may themselves sometimes be "oriented" in the formingthereof as is known in the art to produce molecular or crystalline"orientation".

Wall Portion Preparation

For purposes of the present invention, as wall portion is firstconveniently and conventionally prepared by laminating together at leastone, preferably at least two prepregs of the first type above indicated.The prepregs are arranged interfacially in a first stack preliminarily.The stack arrangement and ordering is, of course, a matter of userchoice, but usually the prepregs comprising the stack are arranged toprovide a maximized strength suitable for the end use applicationintended, as those skilled in the art well appreciate. For example, theunidirectionally extending fibers of one prepreg layer could be arrangednormally relative to the unidirectionally extending fibers in adjacentlayers on either side of such one prepreg, or the like, as desired orchosen.

The stack is positioned between a pair of spaced, preferably (but notnecessarily) parallel molding surfaces, and the mold is closed with themolding surfaces being applied against opposed outside faces of thestack. The molding surfaces are maintained at a temperature which is atleast sufficient to heat fuse together contacting surface portions ofthe thermoplastic resin present in the prepregs. A pressure issimultaneously applied against such opposing stack faces which is atleast sufficient to compress said first prepregs to a predeterminedextent. Such temperature and pressure are concurrently applied for atime which is at least sufficient to heat fuse said first prepregstogether and form the desired wall portion which characteristically andpreferably (but not necessarily) has spaced, parallel opposed surfacesor faces. Thereafter, the mold surfaces are cooled and separated, andthe wall portion separated from the mold.

Thereafter, if desired, the thus formed wall portion can be subjected toa thermoforming operation wherein the surfaces of the wall portion arerelatively mildly contoured into a three dimensional configuration withthe aid of heat and pressure in a conventional thermoforming apparatusso as to produce a desired shaped body having predeterminationprofile(s). In such a profile, the deviations introduced from theinitial plain or flat state of the starting "blank" wall portion istypically relatively small, since care needs to be taken in thethermoforming operation to avoid the application of forces upon thestarting wall portion being thermoformed which are sufficient to damageor even rupture the continuous reinforcing fibers present in thestructure of the starting blank wall portion, such as fiber elongation(and weakening or breaking) or ordered fiber disruption (such as aspreading apart transversely of longitudinally extending unidirectionalfibers or woven fibers, or the like).

Either during such a thermoforming operation itself, or subsequently ina separate operational step, apertures may be cut, if desired, in theformed structure, such as rivet or like fastening holes, portholes orlike window openings, or structurally modifying excisions may be made(for fitting a wall member into a subsequent end use environment), orthe like, as desired. The cutting can be accomplished manually (as whencustom, one-of-a-kind structures are being produced), or by cutting diesin a press arrangement (as when production of a plurality of likestructures is being undertaken, as for repetitive installation andultimate use in a large vehicle or the like), or otherwise as desired.

After preparation, a wall portion can be interveningly stored or movedbefore being used further in accord with the teachings of the presentinvention. For example, wall portions can be made at one location andmoved to another location for association with frame portion(s) inaccord with the present invention.

In addition to thermoforming, a flat composite comprising a blank orprecursor wall portion, can be contour formed by other known procedures.For example, contouring can be accomplished by:

(a) autoclave forming

(b) diaphragm forming as described in "Effect of Forming Temperature onthe Properties of Polymeric Diaphragm Formed Components", C. M.O'Bradaigh and P. J. Mallon, submitted to the ASCM/CCM Joint Symposiumon Composite Materials Science and Engineering (1987);

(c) hydroforming as described in article "Advanced Manufacturing ofThermoplastic Composites" by Kueterman, pages 147-154, AdvancedComposites Conference Proceedings, copyright 1985, and the like.

Wall portion preparation conditions typically involve pressures rangingfrom about 25 to 5,000 pounds per square inch and resin temperatures offrom about 250° to 900° F. applied for times ranging from about 1 minuteto 1 hour. Choice of conditions is dependent upon the thermoplasticresin employed and other factors. For example, when a polyphenylenesulfide resin is employed in the prepregs, the temperatures employed canrange from about 550° to 700° F., preferably 600° -650° F., thepressures can range from about 25 to 1000 psi, preferably 100-150, andthe times can range from about 1 min. to 1 hour.

FRAME FORMATION AND ASSOCIATION WITH WALL PORTION

Next, a second stack of prepregs is laid up on at least onepredetermined location against at least one of the wall surfaces of theso-prepared wall portion. Such second stack is comprised of at least onesecond prepreg, with preferably at least two such prepregs beinginterfacially associated and used when the frame contemplated forcreation is to project prominently outwardly from an associated surfaceof the wall portion, and yet also have a transversely extendingthickness sufficient for the particular structural purposes desired. Thesecond stack in general has prechosen exterior dimensions.

A configuration-defining mold means is positioned exteriorly aroundoutside surface portions of said second stack and also against the other(opposed) side of such wall surfaces at such predetermined location. Theinterrelationship between such second stack and suchconfiguration-defining mold means is such that, when saidconfiguration-defining mold means is pressurized to a predeterminedextent perpendicularly relative to said wall portion, such second stackis consolidated and defines the desired such frame portion. It can beregarded as a feature of the present invention that the second stack ofprepregs as initially cut and placed does not have to have an exteriorconfiguration which is precise since the mold formation pressures aresuch that the prepregs are conformed into the configuration desired.

Once such prepreg lay up and such mold means positioning is completed,the configuration-defining mold means is compressed perpendicularlyrelative to such wall portion with said prechosen pressure (or greateror smaller if desired). Such configuration-defining mold means ispreferably preheated to a predetermined temperature. The prechosentemperature and the prechosen pressure are applied to the second stackat such location for a time at least sufficient to allow for heat fusionto take place between said second prepregs and also to such wallsurfaces at such locations, thereby to produce simultaneously both saidframe portion and also said composite structure.

The configuration-defining mold means is then removed and separated fromthe assembly to leave the desired fabricated integrally formedstructural composite.

In one preferred mode of practicing the process, the frame portion isderived from at least about five second prepregs which are thermallyinterfacially bonded together. Preferably, the frame portion includes anupstanding frame member which projects outwardly from the wall portion adistance which is at least about five times the thickness of the wallportion. Preferably, such a frame portion further includes a laterallyenlarged base member whose cross-sectional area taken parallel to suchwall portion is at least about four times the correspondingly takenaverage cross-sectional area of such upstanding frame member. Such basemember includes a bottom face which is substantially completelythermally bonded to such one face of such wall portion at such location.

In one preferred mode of practicing the invention, the first prepregsused in forming the wall portion have reinforcing fibers arrangedunidirectionally therein, while the second prepregs used in forming theframe portion(s) have reinforcing fibers randomly arranged in a nonwovenmat therein. Similarly, in another preferred mode of practicing theinvention, the first prepregs used in forming the wall portion havereinforcing fibers arranged in a woven fabric therein, while the secondprepregs used in forming the frame portion(s) have reinforcing fiberswhich are substantially continuous and which are randomly arranged in anonwoven mat therein.

Sometimes, herein the term "flattened" is used in characterizing a wallportion. The term "flattened" is used to indicate the fact that a wallportion has generally, but not necessarily, spaced parallel opposingwall surfaces which are not necessarily flat, but indeed may typicallybe curved or curving so that a wall portion when looked upon in end viewor edge wise displays a three-dimensional contour or curvature. Thus,the term "flattened" does not mean planar herein and is distinct from,for example the term "flat".

Similarly, the term "frame" is used herein to embrace allthree-dimensional projections or ribs which can be heat laminated to awall portion. Thus, the term "frame" is inclusive of various functionalcomponents or projections including supports, ribs, projections, joints,brackets, flanges, platforms, and the like, as those skilled in the artwill appreciate.

Conditions employed for frame portion formation and integral associationwith wall portion typically involve pressures ranging from about 1000 to60,000 pounds per square inch, tool (or mold) temperatures ranging fromabout 250° to 900° F. and times ranging from about 1 minute to 3 hours.Choice of conditions is dependent upon the thermoplastic resin employedand other factors. For example, when a polyphenylene sulfide resin isemployed in the prepregs, the tool (or mold) temperatures employed canrange from about 250° to 400° F., the pressures can range from about2500 to 15,000 psi, and the times can range from about 1 to 30 minutes.As in the case of the combination of conditions employed in wall portionformation (see above), the heat/pressure/time relationship is chosen soas to be at least great enough to carry out heat fusion of thethermoplastic resin at all contacting locations, but not great enough toachieve in the thermoplastic resin a level of fluidity such that adisruption or change occurs in the product structural composite inrelation to the starting interrelationship or distribution ofreinforcing fibers in the starting prepreg. For instance, in the productstructural composite, the reinforcing fibers are preferably distributedthroughout the composite; preferably, there are no areas where the resinhas collected or flowed and separated from the fibers. The combinationof conditions is such that the starting composition of the thermoplasticresin has preferably not undergone degradation, although it is commonfor the combination of conditions to cause some thickening andcross-linking of the thermoplastic resin which in some instances isdesired by users of prepregs. In general, the achievement of aparticular combination of heat, pressure, and time is selected through abrief trial or test program for a given product structural composite, asthose skilled in the art will readily appreciate. The availabilty andwidespread use of the contemporary commercially available pressstructures has made possible a wide range of composite formingconditions with usage of significant variations in each of time, moldtemperature, and mold pressure from one part formation to another.

THE MOLD STRUCTURE

The configuration-defining mold structure provided by this invention forthe fabrication of integrally formed structural composites can beregarded as being comprised of three components.

One component is a base member which has a generally smooth workingsurface defined therein whose topographical surface characteristics onareas thereof to be used for object forming purposes mirror the surfacecharacteristics desired on wall portions of an integral compositestructure desired.

A second component is a top member having the reverse exteriorconfiguration of a desired frame structure defined in a working surfacethereof provided that all cavities thus defined therein have side wallswhich are at an angle of less than 90° with respect to the adjacenthorizontal surface portions of said working surface thereof.

A third component is a spacing means adapted for being positioned arounda prechosen perimeter of the desired frame structure to be formed andbetween the base member and the top member. The third component inparticular can be comprised of more than one member for reasons of easeof fabrication and/or use, as those skilled in the art will appreciate,but one member is presently preferred for use as the third component.

These mold components are generally formed of metal, preferably steel orthe like, by machining or the like.

Depending upon the application involved, the base member can beclassified as being either one of two types. In one type, the basemember has a size sufficient to exceed the perimeter of the wallportion, so that, for example, if desired, the perimeter of the basemember can incorporate an upstanding flange, or the like, therebydefining a pocket or flattened recess adapted to receive therein theentire base member. Such a base member can be desirable in use invarious situations, such as in testing and evaluation, and in situationswhere precise component positioning is desired, and the like.

In the other type, the base member has a size which is insufficient toreach the perimeter of the wall portion. Indeed, the base member may beso small relative to the total size of the wall portion as to occupyonly the specified location area intended for use in creating the frameportion plus a small additional circumferential area. With this type ofbase member, an associated working framework is necessary in order toposition such base member accurately at the specified location on oneside of the wall portion while permitting the positioning of the topmember and the spacing component(s) accurately on the opposing side ofthe wall portion in a desired registration relationship therebetween sothat the molding temperatures and pressures can be applied as desired toform the frame member and to heat bond such to the wall portionconcurrently.

Particularly in the case where the structural composite product beingformed has a contoured wall surface in the region where the frameportion(s) are to be formed and integrally associated with the preformedwall portion, it is necessary to make mold components which have workingsurfaces which are curved to mate with the curvatures involved. It canbe regarded as one of the advantages of the present invention that theframe portion(s) can be formed even when relatively significant wallportion curvatures are locally involved at the location or site of frameportion association by using only melt fusion temperatures and formationpressures applied approximately perpendicularly relative to the wallportion at such location of frame portion formation (or perpendicularlyto the projecting frame member being formed in a frame portion).

FIGURE DESCRIPTION

Referring to FIG. 1, there is seen an isometric view of one embodimentof a structural composite produced in accordance with the teachings ofthe present invention which is herein designated in its entirety by thenumeral 20. The embodiment 20 incorporates a wall portion 21 and a frameportion 22. The frame portion 22 and the wall portion 21 are integrallyassociated with one another to provide a one-piece, integral, laminatedstructural composite. In this structure, the wall portion of 21 isgenerally continuous and generally flattened; however, the frame portionis three-dimensional with the frame portion 22 being associated with alimited region 23 of the wall portion 21.

The wall portion 21 is comprised of at least two interfacially thermallybonded first prepregs (such first prepregs having been hereinabovedescribed). In the present situation, each such first prepreg is shownto have a fiber reinforcement which is comprised of continuous wovenglass fibers. The appearance of one surface of the wall portion 21 isillustrated by the enlarged circular magnified view 24. Theresin-covered, slightly raised areas on the surface 26 of wall portion21 are observable. In this embodiment, each of the first prepregs, ingeneral, comprises a thermoplastic resin matrix which is impregnatedwith substantially continuous reinforcing fibers which are arranged inan ordered array.

The appearance of surface portions of the frame portion 22 isillustrated by the circular magnification view 25 which illustrates theappearance of the flattened upper surface of the base member 28 undermagnification. In this embodiment, the second prepregs used to form theframe portion 22 are here comprised of continuous, randomly arrangedreinforcing fibers which are observable as resin covered slightly raisedareas in the surface of the frame portion 22.

The frame portion 22 is here comprised of at least one second prepreg.The frame portion 22 includes an upstanding frame member 27 whichprojects outwardly from the face 26 of the wall portion 21. The frameportion 22 further includes a generally flattened base member 28 whichis formed with the frame member 27 and is integrally associatedtherewith. The base member 28 includes a bottom face (not shown inFIG. 1) which is substantially completely thermally bonded to thelocation 23 on face 26 of wall portion 21.

The embodiment 20 is formed by the technique or process herein describe.The composition of the thermoplastic resin and of the reinforcing fibersis herein above explained. In the embodiment 20, the frame portion 22 ispreferably comprised of at least 2 interfacially thermally bonded secondprepregs, and more preferably of at least 5 interfacially bonded secondprepregs. The frame portion 22 typically can project if desiredoutwardly from the wall portion 21 by a distance which is at least about5 times the thickness of the wall portion 21. The flattened base member28 is positioned between the upstanding frame member 27 and the wallportion 21. The base member 28 has a cross sectional area takenparallelly to the wall portion 21 which is at least about 4 times thecorrespondingly taken average cross-sectional area of the upstandingframe member 27. The bottom surface of the flattened base member 28comprises the bottom face thereof.

To prepare embodiment 20, the wall portion 21 is first prepared bylaminating together the first prepregs. Thereafter, the wall portion 21is positioned in the depressed central area or well 31 of a mold basemember 32 as shown in FIG. 5. In fact, if desired, as a matter ofpreparation convenience, the wall portion 21 can be formed, if desired,by positioning appropriately presized first prepregs in the well 31 andconventionally applying thereagainst the opposing face of a stamp moldmating member (not shown), as those skilled in the art will appreciate.The bottom face of the well 31 has a generally smooth and flat workingsurface defined therein, as shown, for example, in FIG. 5.

In addition to base member 32, the mold structure 29 (see FIG. 2)further includes a top mold member 33 which member 33 has a reverseexterior working surface configuration generally designated by thenumeral 34 in which the reverse or mirrored surface portions desired fora frame portion 22 are defined. All cavities, such as cavity 36 inprojection 44 of surface 34, which cavity 36 has sidewalls 38, extend atan angle which is less than about 90 degrees with respect to theadjacent horizontal surface portions, such as portions 37 of the workingsurface 34; otherwise, as those skilled in the art will appreciate, themold top member 33 cannot be separated from a wall portion 21 formedtherewith.

In addition, the mold structure for forming the frame portion 22includes spacing member means which in the three component moldstructure 29 is provided by the spacer block 39. The spacer block 39 isadapted for positioning around a prechosen perimeter for the framestructure for frame portion 22 with such prechosen perimeter beingdefined by the rectangular aperture 41 defined in the spacer block 39.

In addition, the transverse thickness designated by the letter P inspacer block 39 is chosen so as to provide a height approximatelycorresponding to the height of the frame member 27 in the frame portion22 with opposed faces 42 (the bottom face not being shown) of the spacerblock 39 being adapted for positioning between the horizontal surfaceportions 37 of the top member 33 and the horizontally extending rimsurface portions 43 of the base member 32.

The vertical height of those portions of top member 33 which define theframe member 27 and the upper face of the base member 28 have a verticaldistance or height designated by the letter H which is shorter than thevertical distance P and J associated with the transverse thickness ofthe spacer block 39. By these dimensional considerations, and asdesired, the top member 33 during formation of a frame portion 22therewith does not completely become fully nestably received within thespacer block 39, so that, for example, the rim portion of top member 33does not engage the rim portion of the adjacent spacer block 39, therebypermitting, during the formation of the frame portion 22 with heat andpressure, the continuing application and maintenance of a desired levelof pressure upon the forming frame portion 22 through the use ofpressure perpendicularly applied against the outside face of the moldtop member 33 and the outside bottom face of the mold base member 32.

Referring to FIGS. 3 and 4, there is seen the appearance of theembodiment 20 during its formation in the three component mold structure29. The diagrammatic lines associated with, respectively, the wallportion 21 and the frame portion 22 illustrate the circumstance that theframe portion 22 is formed of randomly arranged fibers while the wallportion 21 is formed with ordered fibers.

The assembled configuration of the three component mold structure 29 isshown or illustrated in FIG. 2 wherein the spacer block 39 rests in thedesired assembled relationship on top of the working surface of the moldbase member 32 while the mold top member 33 is nestably received withinthe block 39. Typically, in the assembled configuration, the opposingsurface of the mold top member 33 in relation to the adjacent surface ofthe spacer block 39 is spaced slightly as shown by the space 46 shown inFIG. 2.

Referring to FIG. 7, there is seen a perspective view of one embodimentof a three-dimensional structural composite produced in accord with theteachings of the present invention. The embodiment 51 shown here is asidewall panel of an aircraft interior, and includes a wall portion 52and various frame portions, identified as 54 and 55, respectively, allframe portions being integrally bonded to the wall portion 52.

The side wall panel 51 is made by the following procedure. First, a flatblank for a wall portion 52 is prepared by laminating together with heatand pressure at least two prepregs of the first type. Next, the blank isthermoformed into the three dimensional, contoured configurationgenerally shown in FIG. 7. Either during the thermoforming operation,or, subsequently, in a separate operation, such as a die cuttingoperation, a window aperture 57 is cut in the crown region of thethermoformed wall portion 52. Thereafter, the resulting thermoformedwall portion 52 is positioned on the base member 58 as shown in FIG. 6of a three piece mold assembly 59, such base member 58 having a workingsurface 56 that is adopted to accommodate and match the concave surfaceof the wall portion 52.

The spacer block 60 of assembly 59 is then positioned over wall portion52 and base member 58. The charge wells 65 defined in spacer block 60are then each charged with pre-cut prepregs of the second type.Thereafter, the top member 61 of assembly 59 is closed against spacerblock 60 with the projections 63 on the working surface 62 of top member61 coming into mating engagement with the charge well 65. Locating pins66 on surface 62 engage receiving holes 67 in spacer block 60 forguiding top member 61 relative to spacer block 60 during mold assembly59 opening and closing operations in the press (not shown). After thecompressing together in registration of the mold elements 61, 60 and 58at elevated temperature and pressure for the desired time, the moldassembly 59 is opened and the finished embodiment 51 removed.

EXAMPLES

A further understanding of the present invention can be obtained byreference to the following specific examples which are provided hereinfor purposes of illustration only and are not intended to be limitingunless otherwise specified.

EXAMPLE 1

To produce for study, test and evaluation purposes an embodiment of theinvention such as shown in FIG. 1, a mold assembly such as shown inFIGS. 2 and 5 was made, and such mold assembly had the followingdimensions (referring to the alphabetical reference letters marked inFIG. 5):

    ______________________________________                                                       Dimension                                                      Reference Letter inches  centimeters                                          ______________________________________                                        A                11.88   30.18                                                B                11.88   30.18                                                C                15.00   38.10                                                D                3.55    9.02                                                 E                3.53    8.97                                                 F                2.48    6.30                                                 G                2.49    6.32                                                 H                2.68    6.81                                                 J                2.89    7.34                                                 K                12.00   30.48                                                M                12.00   30.48                                                O                11.88   30.18                                                P                2.89    7.34                                                 R                6.00    15.24                                                ______________________________________                                    

The mold was fitted with U-shaped centering and securing means attachedto opposing sides of the respective base and top sections 32 and 33 foraligning and for associating therewith the center section or spacerblock 39. The top section 33 was joined to the center section 39 onopposing sides by means of a pair of flexible elbows. Extension of theelbows separated the top and center sections with sufficient distance orspacing to permit placement of starting prepregs into the center moldsection 39 and to permit removal of molded embodiments 20 therefrom.Each section of the mold was fitted with one-half inch diameter holesfor positioning in each hole a 1,000 watt electrical "Watlow" cartridgeheater for maintaining a desired temperature. The mold assembly wasadopted for positioning in a Lawton press Model No. 300 Ton.

EXAMPLE 2

Using the mold of Example 1 positioned in a 300 ton Lawton Press ModelNo. 300 Ton, the base section 32 was heated to 420° F., the spacer block39 was heated to 350° F., and the top member 33 was heated to 325° F.

A 6 inch (15.24 centimeter) by 6 inch (15.24 centimeter) by 0.06 inch(0.15 centimeter) composite is prepared as a wall portion by laminatingtogether 5 prepregs. Each of these prepregs comprises a polyphenylenesulfide impregnated carbon fiber fabric prepreg (constituting a firstprepreg type as such terminology is described and defined herein). Suchprepreg is available commercially under the trade designation "RYTON PPSAdvance Composite AC32-60" from Advanced Composites division of Phillips66 Company, Bartlesville, Okla. 74004. For making this flat composite,the following formation conditions were used: Pressure - about 100 psi,temperature (preheated mold) -about 625° F., time - about 6 minutes.

Concurrently, seven layers of a second prepreg type as such terminologyis described and defined herein were prepared. The prepreg used isavailable commercially under the trade designation "RYTON PPS AdvanceComposite AG20-40" from Advanced Composites division of Phillips 66Company, Bartlesville, Okla. 74004 and which is polyphenylene sulfideimpregnated with continuous, randomly arranged glass fibers, areprepared. Each layer measured 3.50 inches (8.89 centimeter) by 2.50inches (6.35 centimeters) by 0.06 inch (0.15 centimeter). All layerswere preheated in an infrared oven at 840° F. for 2 minutes. Thispreheating caused the fibers in each prepreg piece to relax from theinitial compressed configuration resulting in a thickening (or swellingor lofting) of the individual prepreg pieces from their initialthickness of about 2 millimeters to a final thickness of about 7millimeters each. The so preheated and lofted prepreg pieces are stackedinterfacially on top of one another and deposited in the center sectionor spacer block 39 central aperture 41 with the block 39 being locatedin place on the base member 32. The top member 33 was then closedagainst the spacer block 39 in registration and a pressure wasperpendicularly applied against the opposing faces of the assembled moldassembly 29 of 30 tons for 5 minutes time. The mold assembly 29 was thenopened and the integrally formed wall portion and frame portioncomprising embodiment 20 was removed.

In the product embodiment, the frame portion was found to be well formedand to be fiber reinforced throughout its structure. The frame portionwas bonded at its base uniformly to the wall portion.

EXAMPLE 3

The procedure of Example 2 is repeated except that in place of the"RYTON PPS Advance Composite AG20-40" prepreg material which is likewisecommercially available from the same source and which is polyphenylenesulfide impregnated with randomly arranged glass reinforcing fibers ofabout 1 inch in average length. The preheating time for these matprepreg pieces was 0.83 minutes in the infrared oven. All otherprocessing conditions were unchanged.

In the product embodiment, the frame portion was found to be well formedand to be fiber reinforced throughout its structure. The frame structurewas bonded at its base uniformly to the wall portion.

EXAMPLE 3

The procedure of Example 2 is repeated except that in place of the"RYTON PPS Advance Composite AG20-40" prepreg material there wassubstituted the "RYTON PPS Advancec Composite AC10-20" prepreg materialwhich is likewise commercially available from the same source and whichis polyphenylene sulfide impregnated with randomly arranged glassreinforcing fibers of about 1 inch in average length. The preheatingtime for these mat prepreg pieces was 0.83 minutes in infrared oven. Allother processing conditions were unchanged.

In the product embodiment, the frame portion was found to be well formedand to be fiber reinvorced throughout its structure. The frame structurewas bonded at its base uniformly to the wall portion

ILLUSTRATIVE EXAMPLE 4

The following examples are intended to be illustrative of the practiceof the invention using prepregs similar to those above exemplified, butcomprised of alternative thermoplastic resins within the scope of thepresent invention.

Prepregs of each of the first type and of the second type arecommercially obtained which are based upon each of the followingtrademarked thermoplastic resins:

1. polyetheretherketone from ICI Amercias

2. polyether sulfone from ICI Amercias

3. polyamide imide from Amoco Performance Products

4. polyether ketone from ICI Americas

5. polyether imide from General Electric Company

6. polyarylsulfone from Amoco Performance Products

Using the procedure generally described in Example 2, but employingpressures ranging from about 2500 to 60,000 psi and temperatures rangingfrom about 200° to 600° F., a series of structural composites areprepared using such first and second prepreg types.

Each product structural composite is found to achieve good thermalbonding between the wall portion and the frame portion, and each frameportion is acceptable and has substantially uniform fiber reinforcement.

Having now fully described the invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit or scope of the inventionas set forth herein.

That which is claimed is:
 1. A process for fabricating an integrallyformed structural composite comprised of a generally flattened wallportion and at least one three-dimensional frame portion, said wallportion being derived from at least one first prepreg, and said frameportion being derived from at least one second prepreg,each of saidfirst prepregs comprising a thermoplastic resin matrix which isimpregnated with substantially continuous reinforcing fibers which arearranged in an ordered array in such first prepregs, said at least onesecond prepreg comprising a thermoplastic resin matrix which isimpregnated with reinforcing fibers which are at least about 1/8 inch inaverage length and which have an average diameter to length ratio whichare at least about 1:10, said reinforcing fibers being randomly arrangedin such second prepreg, said thermoplastic resin being selected from theresin group consisting of:polyarylene sulfides, polyethers, polyketones,polysulfones, polyamides, polyimides, polyamideimides, polyetherimidespolyesters, polycarbonates, and acetal resins, said reinforcing fibersbeing comprised of a material selected from the group consistingof:carbon, aramid, glass, quartz, silicon carbide, ceramic, metal coatedcarbon, and metal, said process comprising the steps of:(A) laminatingtogether a first stack of prepregs positioned between a pair of spaced,generally parallel molding surface means applied against opposingoutside faces of said first stack, said first stack comprising said atleast one first prepreg interfacially arranged, said laminating beingcarried out while said molding surface means:are maintained at atemperature which is at least sufficient to heat fuse togethercontacting surface portions of said thermoplastic resin, apply apressure against opposing outside faces which is at least sufficient tocompress said first prepregs to a predetermined extent, said temperatureand said pressure being concurrently applied for a time which is atleast sufficient to heat fuse said first prepregs together, thereby toform said wall portion, said wall portion having generally spaced,parallel, opposed surfaces,(B) laying up a second stack of prepregs on apredetermined location against one of said wall surfaces, said secondstack being comprised of said at least one second prepreg, said secondstack having prechosen exterior dimensions, and positioningconfiguration-defining mold means exteriorly around outside surfaceportions of said second stack and also against the other of said wallsurfaces at said predetermined location, the interrelationship betweensaid second stack and said configuration-defining mold means being suchthat, when said configuration-defining mold means is pressurized to apredetermined extent perpendicularly to said wall portion, such secondstack is consolidated and defines said frame portion, and (C)compressing said configuration-defining mold means perpendicularlyrelative to said wall portion with a prechosen pressure, saidconfiguration-defining mold means being heated to a prechosentemperature, and maintaining said prechosen pressure and said prechosentemperature for a time at least sufficient to heat fuse together saidsecond prepregs to one another and to said wall surfaces at saidlocation, thereby to produce simultaneously said frame portion and alsosaid integral composite structure.
 2. A process of claim 1 wherein saidreinforcing fibers in said second prepreg are at least about 1 inch inaverage length and have a diameter to length ratio of at least about1:15.
 3. A process of claim 1 wherein said frame portion is derived fromat least about two second prepregs which are thermally interfaciallybonded together.
 4. A process of claim 1 wherein said frame portion isderived from at least about five second prepregs which are thermallyinterfacially bonded together.
 5. A process of claim 1 wherein saidframe portion includes an upstanding frame member which projectsoutwardly from said wall portion a distance which is at least about fivetimes the thickness of said wall portion, further includes a laterallyenlarged base member whose cross-sectional area taken parallelly to saidwall portion is at least about four times the correspondingly takenaverage cross-sectional area of said upstanding frame member, said basemember including a bottom face which is substantially completelythermally bonded to said one face of said wall portion at said location.6. A process of claim 1 wherein, in said first prepregs, saidreinforcing fibers are arranged unidirectionally, and wherein, in saidsecond prepregs, said fibers are arranged in a nonwoven mat.
 7. Aprocess of claim 1 wherein, in said first prepregs, said reinforcingfibers are arranged in a woven fabric comprised thereof, and wherein, insaid second prepregs, said fibers are substantially continuous and arearranged in a nonwoven mat.
 8. A process of claim 1 wherein saidthermoplastic resin comprises a polyarylene sulfide selected from thegroup consisting of polyphenylene sulfide, polyphenylene sulfide ketone,polyphenylene sulfide sulfone, poly biphenylene sulfide, and mixturesthereof, and said reinforcing fiber is selected from the fiber groupconsisting of carbon fibers, glass fibers, and aramid fibers.
 9. Aprocess of claim 1 wherein said thermoplastic resin comprises apolyether selected from the group consisting of polyarylethers,polyether ketones, polyetherether ketones, polyether diketones,polyether sulfones, and polyether imides, and said reinforcing fiber isselected from the fiber group consisting of carbon fibers, glass fibers,and aramid fibers.
 10. A process of claim 1 wherein between said step(A) and said step (B), said wall portion is contoured.